Always-on wireless internet protocol communication

ABSTRACT

In accordance with the teachings described herein, systems and methods are provided for always-on wireless IP communication. An access provider network (APN) that includes an always-on packet data serving node (PDSN) may be used to communicate over a wireless communication link with a mobile station. The PDSN may include an inactivity timer and may be used to set the inactivity timer to an inactivity timer starting value and send a starting value estimate to the mobile station over the wireless communication link, wherein the starting value estimate is a function of the inactivity timer starting value. The mobile station may include an inactivity timer estimate and may be used to receive the starting value estimate and set the inactivity timer estimate to the starting value estimate. The mobile station may also be used to reset the inactivity timer estimate to the starting value estimate when the mobile station communicates with the APN.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and is related to the followingprior applications: “Always-On Wireless Internet ProtocolCommunication,” International Application No. PCT/CA2003/001160, filedJul. 31, 2003, which claims priority to “System and Method of WirelessAlways-On Internet Communication,” U.S. Provisional Application No.60/400,865, filed Aug. 1, 2002. These prior applications, including theentirety of the written descriptions and drawing figures, are herebyincorporated into the present application by reference.

FIELD

The technology described in this patent document relates generally tothe field of point-to-point communication techniques. More particularly,the patent document describes a system and method for always-on wirelessinternet protocol (IP) communication with a mobile station, such as a2-way paging device, a cellular telephone, a laptop computer, or othertype of wireless-enabled device.

BACKGROUND AND SUMMARY

Wireless IP networks are known in this field. One such wireless networkis described in the “CDMA2000™ Wireless IP Network Standard,”TIA/EIA/IS-835-B. The CDMA2000™ Wireless IP Network utilizes a linkcontrol protocol (LCP) to establish and configure the point-to-pointprotocol (PPP), which is described in Request for Comments (RFC) 1661.TIA/EIA/IS-835-B and RFC 1661 are incorporated into the presentapplication by reference.

In accordance with the teachings described herein, systems and methodsare provided for always-on wireless IP communication. An access providernetwork (APN) that includes an always-on packet data serving node (PDSN)may be used to communicate over a wireless communication link with amobile station. The PDSN may include an inactivity timer and may be usedto set the inactivity timer to an inactivity timer starting value andsend a starting value estimate to the mobile station over the wirelesscommunication link, wherein the starting value estimate is a function ofthe inactivity timer starting value. The mobile station may include aninactivity timer estimate and may be used to receive the starting valueestimate and set the inactivity timer estimate to the starting valueestimate. The mobile station may also be used to reset the inactivitytimer estimate to the starting value estimate when the mobile stationcommunicates with the APN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example wireless IP communication system that supportsalways-on communication with a mobile station;

FIG. 2 shows example protocol stacks at various components of the systemof FIG. 1;

FIG. 3 shows a block diagram of an example always-on mobile station;

FIG. 4 shows a block diagram of an example always-on PDSN;

FIG. 5 shows a more-detailed block diagram of the example always-on-PDSNof FIG. 4;

FIGS. 6-8 are flow diagrams that illustrate an example operation of analways-on mobile station; and

FIG. 9 is a flow diagram illustrating an example operation of analways-on PDSN.

DETAILED DESCRIPTION

With reference now to the drawing figures, FIG. 1 shows an examplewireless IP communication system that supports always-on communicationwith a mobile station 10. The communication system includes an always-ontarget visited access provider network (VAPN) 12, an always-on servingVAPN 20, back-end network infrastructure 60, 70, 80, and an end host 40.Also included in the illustrated communication system are an IP network30, such as the Internet, and a broadband telecommunications network 50,such as an SS7 network.

In operation, the always-on mobile station (MS) 10 communicates over theIP network 30 with the end host 40 via at least one always-on VAPN 12,20 cooperating with back-end infrastructure 60, 70, 80. The mobilestation 10 is always-on in the sense that a packet data session, such asa point-to-point protocol (PPP) session, may be maintained between themobile station 10 and an always-on access provider network (APN) 12, 20,60 while the mobile station 10 is dormant (e.g., does not have any datato send or receive). In addition, the PPP session may be maintainedduring periods when the mobile station 10 has moved out of coverage oris otherwise temporarily out of communication with the APN 12, 20, whichmay include periods when the mobile station 10 is being serviced by anetwork that does not support data communications.

The always-on target VAPN 12 includes a target radio network (RN) 14 andan always-on target packet data serving node (PDSN) 16. The always-onserving VAPN 20 includes a source radio network (RN) 22, an always-onserving PDSN 25, a remote authentication dial in service (RADIUS) server24, and a mobile switching center (MSC) 23. Preferably, the mobilestation 10 communicates with the always-on target VAPN 12, and is thenhanded-off to the always-on serving VAPN 20 for communication with theback-end infrastructure 60, 70, 80 and the end host 40. Alternatively,however, the mobile station 10 could communicate with back-endinfrastructure directly via the always-on serving VAPN 20.

The always-on target PDSN 16 and/or the always-on serving PDSN 25 areconfigured to support always-on service for the mobile station 10. Thealways-on serving PDSN 25 preferably cooperates with the mobile station10 via the always-on target PDSN 16. Alternatively, however, only one ofthe target PDSN 16 or the serving PDSN 25 may be an always-on PDSN. Adetailed description of the always-on service, including descriptions ofthe always-on mobile station 10 and the always-on PDSN 16, 25, isprovided below with reference to FIGS. 2-9.

The radio network (RN) 14, 22 may include a base station(s) to provideRF communication with the mobile station 12 and may also include apacket control function (PCF) to communicate with the always-on PDSN 16,25. The communication link between the RN 14, 22 and the PDSN 16, 25 maybe an R-P interface that uses a GRE tunnel to transport user packet dataand signaling messages between the PCF and PDSN 16, 25. Thecommunication link between the target PDSN 16 and the serving PDSN 25may be a P-P interface to transport user data for a single serviceinstance, and may be used to support a fast handoff function.

The RADIUS servers 24, 74, 84 located in the serving VAPN 20, home IPnetwork 74 and broker network 84 are authentication, authorization andaccounting (AAA) servers, such as those typically used in CDMA2000™networks for providing AAA functionality. The home IP network 70 andhome RADIUS server 74 provide IP based data services to the mobilestation user, such as maintaining a network access identifier (NAI) forthe mobile station 10. The broker network 80 and broker RADIUS server 84is an intermediate network/server(s) that may be used to securelytransfer RADIUS messages (e.g., AAA information) between the VAPN RADIUSserver 24 and the home RADIUS server 74. It should be understood thatmore than one broker RADIUS server 84 may be used to transfer databetween the VAPN RADIUS server 24 and the home RADIUS server 74.

The mobile switching center (MSC) 23 connects the source RN 22 with ahome location register (HLR) 62 at a home access provider network (APN)60. The home access provider network 60 is a wireless network thatprovides the home service area for the mobile station 10. It should beunderstood that the system illustrated in FIG. 1 shows an exampleoperation of the always-on mobile station 12 while the mobile station 12is outside of the coverage area of the home access provider network 62.However, the home access provider network 60 preferably includes similarcomponents as the visited access provider network 12, 20, including ahome radio network (RN) and a home always-on PDSN. Therefore, always-onservice may also be available between the always-on mobile station 12and the home always-on PDSN in the home APN 60.

The example wireless IP communication system illustrated in FIG. 1 may,for example, be a CDMA2000™ wireless IP network that is configured toprovide always-on service, as described herein. Additional detailsregarding the operation of a typical CDMA2000™ wireless IP network maybe found in the following standard documents (referred to herein as the“Standards”): TIA/EIA/IS-835-B, RFC 1661, TIA/EIA/IS-2000-1 (3GPP2C.S0001), TIA/EIA/IS-2000-2 (3GPP2 C.S0002), TIA/EIA/IS-2000-3 (3GPP2C.S0003), TIA/EIA/IS-2000-4 (3GPP2 C.S0004), TIA/ELA/IS-2000-5 (3GPP2C.S0005), TIA/EIA/IS-707 (3GPP2 C.S0017), A.S0001, and their revisions,which are incorporated herein by reference.

FIG. 2 shows example protocol stacks 110, 122, 125, 140 at variouscomponents of the IP-based system of FIG. 1. Four protocol stacks 110,122, 125 and 140 are illustrated, each corresponding respectively to thealways-on mobile station (MS) 10, a radio network (RN) 14, 22, analways-on PDSN 16, 25 and the end host 40. Protocol stacks 110 and 125each include always-on point-to-point protocol (PPP) layers 115 and 130.The always-on PPP layers 115 and 130 co-operate to maintain a PPPsession, which enables IP communication between the mobile station 10and the end host 40 despite out-of-coverage or similar situations at themobile station 10. The operation of the always-on PPP layer 115 at thealways-on mobile station 10 is described below with reference to FIG. 3,and the operation of the always-on PPP layer 135 at the always-on PDSN16, 25 is described below with reference to FIGS. 4 and 5. The operationof the remaining protocol layers illustrated in FIG. 2 is within theknowledge of persons skilled in the art and is described in more detailin the Standards. The physical layer airlink between the always-onmobile station and RN is described in TIA/EIA/IS-2000-2. The MAC betweenthe always-on mobile station and RN is described in TIA/EIA/IS-2000-3.The LAC between the always-on mobile station and RN is described inTIA/ELA/IS-2000-4. The Layer 3 signaling messages used for control ofthe physical layer are described in TIA/EIA/IS-2000-5. The Radio LinkProtocol (RLP) between the always-on mobile station and RN is describedin TIA/EIA/IS-707. The R-P protocol, also known as A10 and A11 isdescribed in A.S0001.

FIG. 3 shows a block diagram of an example always-on mobile station 310,and FIGS. 4 and 5 show block diagrams of an example always-on PDSN 425.Also illustrated in FIGS. 3-5 are example communications 350, 355, 360,370, 380, 390 between the always-on mobile station 310 and the always-onPDSN 425 that may be used to maintain an always-on PPP session.

With reference first to FIG. 3, the example mobile station (MS) 310includes an always-on MS module 315, a processor 320, a transceiver 322,an inactivity timer estimate 330, and other mobile station modules 340.The processor 320 may be a microprocessor, a digital signal processor,or some other type of processing device. The transceiver 322 is operableto transmit and receive RF signals, and may include a single transceivercircuit or separate transmitter and receiver circuits. The always-on MSmodule 315 may be a software module, a hardware module or a combinationof both, and is operable to set and track the inactivity timer estimate330. The inactivity timer estimate 330 may be a timing device, such as adecrementing counter, that is set by the always-on MS module 315 toestimate the value of an inactivity timer 430 in the always-on PDSN 425(see FIGS. 4 and 5). The other modules 340 may be software and/orhardware modules typically included in a mobile station 310, such as adisplay, keyboard, speaker, microphone, etc.

Operationally, when a PPP session 390 is initiated between the mobilestation 310 and an always-on PDSN 425, the PDSN 425 transmits a linkcontrol protocol (LCP) message 350 to the mobile station 310 thatincludes a starting value estimate 355, which is generated by the PDSNas a function of the initialization value for the inactivity timer 430in the PDSN 425. When the mobile station 310 receives the LCP message350, the starting value estimate 355 is used by the always-on MS module315 to initialize the inactivity timer estimate 330, and an LCP replymessage 360 is transmitted from the mobile station 310 to the always-onPDSN 425.

The value of the inactivity timer estimate 330 affects the operation ofthe always-on MS module 315, particularly in out-of-coverage situations.That is, an always-on connection with the PDSN 425 is maintained so longas the inactivity timer estimate 330 has not expired. During periods ofinactivity, the always-on MS module 315 causes the inactivity timerestimate 330 to decrement from the starting value estimate 355. Eachtime a PPP frame is sent or received by the mobile station 310, theinactivity timer estimate 330 is reset to the starting value estimate355. To maintain an always-on connection during periods of inactivity,the always-on MS module 315 may send and receive LCP messages or otherPPP session communications 350, 360, 370, 380 to and from the always-onPDSN 425. Upon expiration of the inactivity timer estimate 330, themobile station 310 may initiate a new PPP session 390, or may enter aninactive state. If a new PPP session 390 is initiated by the mobilestation 310, then the mobile station 310 may receive a new startingvalue estimate 355 from the PDSN 425, or may reset the inactivity timerestimate 330 using the starting value estimate 355 from the prior PPPsession. The operation of the mobile station 310 is further describedbelow with reference to FIGS. 6-8.

With reference now to FIG. 4, the example always-on PDSN 425 includes analways-on PDSN module 415, a processor 420, a transceiver 422, aninactivity timer 430 and other PDSN modules 440. The processor 420 maybe a microprocessor, a digital signal processor, or some other type ofprocessing device. The transceiver 422 may, for example, be a networkcard that is configured to send and receive data over a wireless linkvia a radio network (RN) 14, 22. The always-on PDSN module 415 may be asoftware module, a hardware module, or a combination of both, and isoperable to reset and track the inactivity timer 430. The inactivitytimer 430 may be a timing device, such as a decrementing counter, andmay be used by the always-on PDSN 425 to monitor the amount of timesince a PPP frame was sent to or received from the always-on mobilestation 310.

Operationally, upon entering the IP control protocol (IPCP) opened stateon a PPP session, the PDSN 425 starts the inactivity timer 430, andsends an LCP request message 350 to the mobile station 310 that includesa starting value estimate 355 generated as a function of the startingvalue of the inactivity timer 430. The starting value estimate 355 isused by the mobile station 310 to estimate the value of the inactivitytimer 430, as described above. Then, when the processor 420 in thealways-on PDSN 425 detects PPP activity with an always-on MS 310, thealways-on PDSN module 415 is notified of the activity and resets theinactivity timer 430 to its starting value. PPP activity which may causethe always-on PDSN module 415 to reset the inactivity timer 430 may, forexample, include sending or receiving an LCP request message 350, 370,sending or receiving an LCP reply message 360, receiving an initiatePPP-session 390, or other PPP-session communications with the mobilestation 310.

FIG. 5 shows a more-detailed block diagram of the example always-on PDSN425 that illustrates an Echo-Reply-Timeout timer 460 and anEcho-Request-Retries counter 470, in addition to the components shown inFIG. 4. The Echo-Reply-Timeout timer 460 may be used by the PDSN 425 totrack the amount of time since an LCP request message 350 or Echorequest message 471 was sent by the PDSN 425 with no response from themobile station 310. The Echo-Request-Retries counter may record thenumber of times that the always-on PDSN 425 resends an LCP requestmessage 350 or Echo request message 471 to the mobile station 310without receiving an LCP reply message 360 in response. It should beunderstood that the LCP reply message 360 may be a rejection if, forexample, the mobile station does not support LCP messages 350, such asmay be the case if the LCP message 350 is a vendor specific LCP message.

Upon expiration of the inactivity timer 430, the PDSN 425 may send anEcho-Request message to the mobile station 310 in an attempt to maintainthe PPP session by eliciting an Echo-Reply message from the mobilestation 310. When an Echo-Request message is sent by the PDSN 425, theEcho-Reply-Timeout timer 460 is started, and the Echo-Request-Retriescounter 470 is initialized. If an Echo-Reply message is received fromthe mobile station 310, then the always-on PDSN 425 may reset theinactivity timers 430, and the PPP session is maintained. Otherwise, ifthe Echo-Reply-Timeout timer 460 expires and the Echo-Request-Retriescounter 470 has not reached a pre-selected cutoff value (e.g., zero),then the always-on PDSN 425 may send another LCP Echo-Request message tothe mobile station 310, decrement the Echo-Request-Retries counter 470,and re-start the Echo-Reply-Timeout timer 460. This process may berepeated until an Echo-Reply message or other PPP activity is receivedfrom the mobile station 310 or until the Echo-Request-Retries countervalue reaches the cutoff value, at which point the always-on PDSN 425may close the PPP session. The operation of the always-on PDSN 425 isfurther described below with reference to FIG. 9.

In order to account for the PDSN 425 sending and resending anEcho-Request message upon expiration of the inactivity timer 430, thestarting value estimate 355 transmitted to the mobile station 310 may becalculated as follows:SVE=IT+ERT×(ERR+1),

where SVE is the starting value estimate 355, IT is the starting valueof the inactivity timer 430, ERT is the starting value of theEcho-Reply-Timeout timer 430, and ERR is the starting value of theEcho-Request-Retries counter.

It should be understood, however, that other techniques could be used tocalculate the starting value estimate 355 to provide an accurateestimate.

FIGS. 6-8 are flow diagrams that illustrate an example operation of analways-on mobile station. With reference first to FIG. 6, the methodbegins at step 500, which may occur, for example, when an always-onmobile station is powered on. In step 505, the mobile station initiatesa PPP session. For example, the mobile station may initiate a call usinga packet data service option such as Service Option 33. Further detailsof the PPP session initiation procedure are available inTIA/EIA/IS-2000-1, TIA/EIA/IS-2000-2, TIA/EIA/IS-2000-3,TIA/EIA/IS-2000-4, TIA/EIA/IS-2000-5, and TIA/EIA/IS-707, which havebeen incorporated herein by reference. The PDSN may then open a PPPsession to the mobile station, causing the mobile station to enter theIP Control Protocol (IPCP) Opened state at step 510.

In step 515, the mobile station determines if it has received a messagewith a data field, such as an LCP request message from the PDSN thatincludes a starting value estimate, as described above. It should beunderstood, however, that the mobile station may receive the startingvalue estimate in other ways, such as via an A-interface message in anew version of the A-interface sent from the PDSN to the RN and then tothe MS via a message defined in a new version of IS-707. In any case, ifthe expected message is not received by the mobile station within apre-determined time interval, then the method proceeds to FIG. 8.Otherwise, if a message with the expected data field is received withinthe pre-determined time interval, then the method continues to FIG. 7.

With reference now to FIG. 7, the method continues from FIG. 6. At step600, the inactivity timer estimate in the mobile station is reset. Forexample, if the mobile station had received a starting value estimate of60 seconds in FIG. 6, then the inactivity timer estimate may be set 60and decrement once per second such that it would expire at zero. At step605, the mobile station monitors for PPP activity. If PPP activity isdetected, then the method returns to step 600. Otherwise, if no PPPactivity is detected, then the method continues to step 610. PPPactivity may, for example, be detected by sending or receiving a PPPpacket to or from the PDSN.

At decision step 610, the mobile station determines if a conditionexists to make the mobile device unreachable by the PDSN. An unreachablecondition could, for example, result from losing the paging channel,making a voice telephone call using a service option such as EVRC whenthe air interface does not support concurrent services, or for otherreasons. If there is no condition making the mobile station unreachable,then the method returns to step 605. Otherwise, if there is a conditionthat makes the mobile station unreachable, then the method continues tostep 615.

At decision step 615, the mobile station determines if it has becomereachable by the PDSN. This may occur, for example, if the mobilestation reacquired the Paging Channel after a loss of the pagingchannel, ended a voice telephone using a service option such as EVRC, orfor other reasons. If the mobile station is not yet reachable, then themethod remains at decision step 615. Otherwise, if the mobile stationbecomes reachable, then the method continues at decision step 620.

At decision step 620, the mobile station determines if the inactivitytimer estimate has expired. If the inactivity timer estimate on themobile station has not expired, then processing continues at step 605.If the inactivity timer estimate has expired, however, then the methodcontinues to step 625. At step 625, the mobile station sends an LCPrequest message to the PDSN and awaits a reply. Once the mobile stationreceives an LCP reply from the PDSN in step 630, processing continues atstep 600.

Turning now to FIG. 8, the method continues from FIG. 6. At decisionstep 700, the mobile station determines if a condition exists making themobile station unreachable by the PDSN, as described above withreference to step 610 in FIG. 7. If there is no condition making themobile station unreachable, then the method remains at step 700, and themobile station continues normal operation. Otherwise, if there is acondition that makes the mobile station unreachable, then processingcontinues at step 705. At decision step 705, the mobile stationdetermines if it is again reachable by the PDSN. For example, the mobilestation may become reachable if it reacquires the Paging Channel, ends avoice telephone communication using a service option such as EVRC, orfor other reasons. If the result of decision step 705 is that the mobilestation is not yet reachable, then processing remains at decision step705. If the result of decision step 705 is that the mobile station hasbecome reachable, however, then the mobile station initiates a PPPsession at step 710, and the method repeats.

FIG. 9 is a flow diagram illustrating an example operation of analways-on PDSN. The method begins in step 800 when the PDSN initiates aPPP session with a mobile station. At step 805, the PDSN enters the IPCPOpened state, and processing continues at step 810. At step 810, thePDSN sends an LCP message, such as an Echo-Request message, including adata field of non-zero length that includes the starting value estimate,as described above. Then, at step 815 the PDSN starts (or resets) theinactivity timer. For example, if a value of 60 seconds is used for thestarting value of the inactivity timer, then the PDSN may set theinactivity timer to 60 and decrement the timer once per second such thatit expires at zero.

Once the inactivity timer has been set, the method monitors for PPPactivity at step 820. If PPP activity is detected, then the methodreturns to step 815. Otherwise, if no PPP activity is detected, then themethod continues to step 825. PPP activity may, for example, be detectedby sending or receiving a PPP packet to or from the mobile station. Atdecision step 825, the PDSN determines if the inactivity timer hasexpired. If the inactivity timer has expired, then the method returns tostep 820. Otherwise, the method continues to step 830.

At step 830, the PDSN sends an LCP message, such as an Echo-Requestmessage, to the mobile station. Then, at step 835, the PDSN starts anEcho-Reply-Timeout timer and decrements an Echo-Request-Retries counterby one. At step 840, the PDSN monitors for an LCP Echo-Reply message, anLCP Echo-Request message, or any other PPP data from the mobile station.If a PPP message is received at step 840, then the Echo-Reply-Timeouttimer is stopped at step 845, and the method returns to step 815.Otherwise, if no PPP message is received at step 840, then the methodcontinues to step 850.

At decision step 850, the PDSN determines if the Echo-Reply-Timeouttimer has expired. If not, then the method returns to step 840. If theEcho-Reply-Timeout timer has expired, however, then the method continuesto step 855. At decision step 855, the PDSN determines if theEcho-Request-Retries counter is greater than zero. If the counter isgreater than zero, then the method returns to step 830. Otherwise, ifthe Echo-Request-Retries counter is not greater than zero, then the PPPsession is released at step 860, and the method ends.

This written description uses examples to disclose the invention,including the best mode, and also to enable a person skilled in the artto make and use the invention. The patentable scope of the invention mayinclude other examples that occur to those skilled in the art. Forexample, in one embodiment an always-on APN may include an always-onradio network (RN) that cooperates with the always-on PDSN and always-onmobile station to treat voice communications as PPP activity. Thealways-on PDSN may determine from the always-on RN that the always-onmobile station is currently in a voice call, and therefore that themobile station is unreachable for the purposes of PPP communication. Inthis case, the always-on PDSN may treat the always-on mobile station asif it were active for the purposes of PPP.

1. An always-on wireless internet protocol (IP) network, comprising: an access provider network (APN) including an always-on packet data serving node (PDSN), the APN being operable to communicate over a wireless communication link with a mobile station; the PDSN including an inactivity timer, the PDSN being operable to set the inactivity timer to an inactivity timer starting value and send a starting value estimate to the mobile station over the wireless communication link, wherein the starting value estimate is a function of the inactivity timer starting value; the mobile station including an inactivity timer estimate, the mobile station being operable to receive the starting value estimate and set the inactivity timer estimate to the starting value estimate; and the mobile station being further operable to reset the inactivity timer estimate to the starting value estimate when the mobile station communicates with the APN.
 2. The always-on wireless internet protocol (IP) network of claim 1, wherein the mobile station includes a mobile station module that sets and resets the inactivity timer estimate.
 3. The always-on wireless internet protocol (IP) network of claim 1, wherein the inactivity timer starting value is a maximum value and wherein the PDSN decrements the inactivity timer from the maximum value when there is no data activity on the wireless communication link.
 4. The always-on wireless internet protocol (IP) network of claim 1, wherein the starting value estimate is a maximum value and wherein the mobile station decrements the inactivity timer estimate from the maximum value when there is no data activity on the wireless communication link.
 5. The always-on wireless internet protocol (IP) network of claim 4, wherein the wireless communication link between the mobile station and the APN is maintained until the inactivity timer estimate is decremented to a pre-selected value.
 6. The always-on wireless internet protocol (IP) network of claim 1, wherein if the inactivity timer estimate reaches a pre-selected value, then the mobile station being configured to enter an inactive state.
 7. The always-on wireless internet protocol (IP) network of claim 1, wherein if the inactivity timer estimate reaches a pre-selected value, then the mobile station being configured to establish a new wireless communication link between the mobile station and the APN.
 8. The always-on wireless internet protocol (IP) network of claim 1, where the wireless communication link between the APN and the mobile station is a point-to-point protocol (PPP) session.
 9. The always-on wireless internet protocol (IP) network claim 8, wherein the PDSN is operable to send the starting value estimate to the mobile station upon entering an IP control protocol (IPCP) open state on the PPP session.
 10. The always-on wireless internet protocol (IP) network of claim 1, wherein the PDSN is operable to send an updated starting value estimate to the mobile station if the inactivity timer starting value is modified.
 11. The always-on wireless internet protocol (IP) network of claim 1, wherein the always-on wireless IP network is a CDMA2000 network.
 12. The always-on wireless internet protocol (IP) network of claim 8, wherein starting value estimate is included in a link control protocol (LCP) message transmitted from the APN to the mobile station.
 13. The always-on wireless internet protocol (IP) network of claim 12, wherein the LCP message is an Echo-Request message.
 14. The always-on wireless internet protocol (IP) network of claim 8, wherein the mobile station module resets the inactivity timer estimate to the starting value estimate in response to the mobile station successfully sending an Echo-Reply message to the APN.
 15. The always-on wireless internet protocol (IP) network of claim 8, wherein the mobile station module resets the inactivity timer estimate to the starting value estimate in response to the mobile station receiving an Echo-Request message from the APN.
 16. The always-on wireless internet protocol (IP) network of claim 8, wherein the mobile station module resets the inactivity timer estimate to the starting value estimate in response to PPP activity between the mobile station and the APN.
 17. The always-on wireless internet protocol (IP) network of claim 1, wherein the PDSN includes an always-on PDSN module that is operable to monitor activity on the wireless communication link between the APN and the mobile station and reset the inactivity timer to the inactivity timer starting value if activity is detected.
 18. The always-on wireless internet protocol (IP) network of claim 1, wherein the inactivity timer estimate is equal to the inactivity timer starting value.
 19. The always-on wireless internet protocol (IP) network of claim 8, wherein the inactivity timer is a PPP inactivity timer.
 20. The always-on wireless internet protocol (IP) network of claim 19, wherein the inactivity timer starting value is a maximum PPP timer value.
 21. The always-on wireless internet protocol (IP) network of claim 19, wherein the PDSN is operable to send an LCP request message to the mobile station if the PPP inactivity timer reaches a pre-selected value.
 22. The always-on wireless internet protocol (IP) network of claim 21, wherein the PDSN includes an Echo-Reply-Timeout timer, and wherein the PDSN is operable to reset the Echo-Reply-Timeout timer to an Echo-Reply-Timeout timer starting value and reset the PPP inactivity timer to the inactivity timer starting value if the APN receives a PPP message from the mobile station.
 23. The always-on wireless internet protocol (IP) network of claim 22, wherein the PDSN includes an Echo-Request-Retries counter, and wherein if the Echo-Reply-Timeout counter reaches a pre-determined value, then the PDSN being configured to resend the an Echo-Request message to the mobile station and reset the Echo-Request-Retries counter from a starting value to identify a number of times that the PDSN attempts to send the Echo-Request message to the mobile station without receiving an Echo-Reply message from the mobile station.
 24. The always-on wireless internet protocol (IP) network of claim 23, wherein if the Echo-Request-Retries counter reaches a pre-selected cutoff value, then the PDSN being configured to close the PPP session.
 25. A method of maintaining an always-on wireless communications link between a mobile station and an access provider network (APN), comprising: establishing a wireless communication link between the mobile station and the APN; setting an inactivity timer in the APN to an inactivity timer starting value; sending a starting value estimate from the APN to the mobile station that is a function of the inactivity timer starting value; setting an inactivity timer estimate in the mobile station to the starting value estimate; monitoring the wireless communication link between the mobile station and the APN for data traffic between the mobile station and the APN; and if data traffic is detected, then resetting the inactivity timer estimate in the mobile station to the starting value estimate and resetting the inactivity timer in the APN to the inactivity timer starting value.
 26. The method of claim 25, further comprising: if the inactivity timer estimate reaches a pre-selected value, then establishing a new wireless communication link between the mobile station and the APN or causing the mobile station to enter an inactive state.
 27. The method of claim 25, wherein the wireless communication link is a point-to-point protocol (PPP) session.
 28. The method of claim 27, wherein the starting value estimate is included in a link control protocol (LCP) message transmitted from the APN to the mobile station.
 29. The method of claim 28, wherein the LCP message is an Echo-Request message.
 30. The method of claim 27, further comprising: if the inactivity timer in the APN reaches a pre-determined value, then transmitting a link control protocol (LCP) Echo-Request message from the APN to the mobile station.
 31. The method of claim 30, wherein if the inactivity timer in the APN reaches the pre-determined value, then resetting an Echo-Reply-Timeout timer in the APN.
 32. The method of claim 31, wherein if the inactivity timer in the APN reaches the pre-determined value, then resetting an Echo-Request-Retries counter in the APN.
 33. The method of claim 32, further comprising: monitoring the wireless communication link for an Echo-Reply message from the mobile station; if an Echo-Reply message from the mobile station is detected, then resetting each of the Echo-Reply-Timeout timer, the Echo-Request-Retries counter and the inactivity timer; if the Echo-Reply-Timeout timer reaches a selected value, then incrementing or decrementing the Echo-Request-Retries counter and transmitting an additional LCP Echo-Request message from the APN to the mobile station; and if the Echo-Request-Retries counter is incremented or decremented to a set value and the Echo-Reply-Timeout timer reaches the selected value, then closing the PPP session.
 34. A packet data serving node (“PDSN”) configured to maintain an always-on wireless communication link with a mobile station in a wireless communication network, the PDSN comprising: an inactivity timer, the inactivity timer configured to start upon the PDSN entering a packet data session; a transceiver, the transceiver configured to send a starting value estimate that is a function of an inactivity timer starting value; a processor coupled to transceiver, the processor configured to monitor the always-on wireless communication link between the mobile station and the PDSN for data traffic between the mobile station and the PDSN; and an always-on PDSN module coupled to the processor and the inactivity timer, the always-on PDSN module configured to reset the inactivity timer to the inactivity timer starting value if the processor detects data traffic.
 35. The PDSN of claim 34, wherein the packet data session includes a point-to-point (“PPP”) session.
 36. The PDSN of claim 35, wherein the inactivity timer includes a PPP inactivity timer.
 37. The PDSN of claim 36, wherein the inactivity timer is further configured to start upon the PDSN entering an Internet Protocol control (“IPCP”) opened state on a PPP session.
 38. The PDSN of claim 34, wherein the starting value estimate is the inactivity timer starting value.
 39. The PDSN of claim 34, wherein the inactivity timer starting value is a maximum PPP timer value.
 40. The PDSN of claim 34, wherein the wireless communication network is a CDMA2000 network.
 41. The PDSN of claim 34, wherein the transceiver is further configured to transmit a link control protocol (“LCP”) message that includes the starting value estimate.
 42. The PDSN of claim 41, wherein the LCP message includes an Echo-Request message.
 43. The PDSN of claim 42, wherein the transceiver is further configured to transmit an LCP Echo-Request message if the inactivity timer reaches a pre-determined value.
 44. The PDSN of claim 43, wherein the always-on PDSN module is further configured to initialize an Echo-Reply-Timeout timer if the inactivity timer reaches the pre-determined value.
 45. The PDSN of claim 44, wherein the always-on PDSN module is further configured to initialize an Echo-Request-Retries counter if the inactivity timer reaches the pre-determined value.
 46. The PDSN of claim 45, wherein the always-on PDSN module is further configured to monitor the wireless communication link for an Echo-Reply message, and to reset each of the Echo-Reply-Timeout timer, the Echo-Request-Retries counter and the inactivity timer if the always-on PDSN module detects an Echo-Reply message.
 47. The PDSN of claim 46, wherein: the always-on PDSN module is further configured to increment or decrement the Echo-Request-Retries counter, and the transceiver is further configured to transmit an additional LCP Echo-Request message if the Echo-Reply-Timeout timer reaches a selected value.
 48. The PDSN of claim 47, wherein the always-on PDSN module is further configured to close the session if the Echo-Request-Retries counter is incremented or decremented to a set value and the Echo-Reply-Timeout timer reaches the selected value.
 49. The PDSN of claim 34, wherein: the transceiver is further configured to receive at least one data packet for the packet data session, and the always-on PDSN module is further configured to stop the Echo-Reply Timeout timer and to reset each of the Echo-Reply Timeout timer, the Echo-Request-Retries counter, and the inactivity timer, if the transceiver receives at least one data packet for the packet data session.
 50. The PDSN of claim 34, wherein the at least one data packet is a point-to-point (“PPP”) packet and the packet data session is a PPP session. 